Several intra-corporal expandable devices including, notably, those described in documents U.S. Pat. No. 3,976,060, Proc Inst Mech Eng [H]. 1989; 203(2): 97-102., WO 01/78614, DE 85 15 687 U1 or U.S. Pat. No. 6,336,929 include a first elongated part, a second part assembled telescopically relative to the said first part, first links to the organism at a first end of the said first part, second links to the organism at a first end of the said second part, a rod with at least one thread, the rotation of which causes displacement of the second part relative to the said first part, means for controlling the rotation of the said rod and links between these components. However, in all these known devices the said rod is assembled between the said first end of the said first part, and the second end of the said second part opposite the said first end of the said second part. The said rod is thus assembled between two ends which move apart when the device is elongated, the loaded rod length increases when the device is elongated and the loaded rod length operates under compression when the device is elongated. As a consequence, the length of the elongation is limited by the buckling height of the said rod under the applied load, the volume devoted in the said device to the said rod and to the tapping with which it cooperates which does not contribute to the robustness, notably under deflection, of the said devices, is substantial and, above all, the torque required to rotate the said rod is also substantial, which determines the dimensioning of the means to control the rotation of the said rod accordingly, and restricts usage in practice of certain means which are simple and reliable but of limited power, such as direct magnetic transmission without amplification between two permanent magnets, for example as described in document U.S. Pat. No. 6,336,929.